Tire inflation systems are used on vehicles, such as a tractor-trailer vehicle, to maintain tire inflation pressures at a desired tire pressure setting. The tire inflation system draws pressurized air from on-board air tanks that also supply pressurized air to other vehicle systems, such as brake and suspension systems. The tire inflation system includes a control that automatically supplies air from one of the on-board air tanks to an under-inflated tire when tire pressure falls below the desired tire pressure setting.
Tire pressures can change during vehicle operation for many different reasons. The tire could have a slow leak caused by an embedded nail or a small puncture. Tire pressure can also change in response to changes in ambient temperature. Increasing the ambient temperature increases tire pressure and decreasing the ambient temperature decreases tire pressure.
For example, assume a tractor-trailer starts out in Florida, where the ambient temperature is 100° F., and drives to Minnesota where the ambient temperature is 0° F. This 100 degree decrease in ambient temperature will cause an approximate 20 psi decrease in tire pressure. In this situation, the tire inflation system will add air to the tires in response to the change in temperature as it would if there were a tire leak caused by a nail.
However, if the tractor-trailer starts out in Minnesota where the ambient temperature is 0° F., and drives to Florida, where the ambient temperature is 100° F., the tire inflation system does not typically respond accordingly. The 100 degree increase in ambient temperature will cause an approximate 20 psi increase in tire pressure. Traditionally, tire inflation systems, such as those used on commercial tractor-trailer vehicles, do not have a way of deflating over-inflated tires. Thus, the tire inflation system does not react when the tires are pressurized higher than the desired tire pressure setting and a vehicle operator may think that the tire inflation system is not operating properly.
It would be beneficial to provide a tire inflation system with a simple and effective way to control excessive tire pressure in addition to maintaining tire pressure at a desired tire pressure setting.